Paul, If the OA2 is going dark on transmit it means the circuit is going out of regulation, so there's probably lots of ripple on what is supposed to be a regulated DC voltage. That could be the source of your bad audio reports. The OA2 is a shunt regulator and will dim with increased current draw, but it shouldn't go out. You could have some dry or leaky electrolytic capacitors and/or some resistors that have changed value.
73, Bob AD3K -----Original Message----- From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Paul Gerhardt Sent: Tuesday, November 01, 2011 4:34 PM To: drakelist@zerobeat.net Subject: Re: [Drakelist] Drakelist Digest, Vol 40, Issue 59 > Message: 1 > Date: Mon, 31 Oct 2011 14:11:50 -0400 > From: Paul Gerhardt <phgerha...@gmail.com> > To: drakelist@zerobeat.net > Subject: Re: [Drakelist] T4XB Poor Transmit > Message-ID: > <CACkHHUKmP8yzoF=qkcexxuu4q5bf-rb3hrstbykeiyrq_h+...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Still playing with swapping the power supplies and today got a 'good' > audio report with the AC-3. I noticed that the OA2 dims a bit with > the AC3 but goes dark on transmit with the AC4 (which gave 'bad' audio > report). Does anyone know what the normal 'look' of the OA2 is when > switching into Transmit? > > Next the meter will come out to check the voltages. What are normal > ripple reading on a modern DVM? > OK this page has a good rundown on checking the P/S voltages http://www.wb4hfn.com/DRAKE/DrakeArticles/TechTips/PowerSupplyTroubleshootin g.htm Basically it says: 2V AC or less on the 700V B+ 1VAC or less on the 250V B+ .5V or less on the bias On the original stock AC-3 I am getting LOTS of AC on the 700V DVM is jumping between 3hundred something and 4 hundred something. Old Radio Shack Analog meter pegs on the 1000VAC scale?! Yet Audio still sounds at least OK?! 4VAC on the 250V line .9VAC on the bias line So at least one of the HV Caps is probably bad. The transformer is pretty warm too after a few hours. I can hold my hand on it but after 30 sec or so it is uncomfortably warm maybe 120-130F. This is probably warmer than it should be as the unit is not transmitting. As the AC-4 is receiving Bad Audio reports and the AC-3 is not I think both supplies must be in need of recapping. Well they are both close to 50 years old. Will put the meter on the AC-4 later. _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
